Cell phones provide mobile coverage over a limited geographic area. There is a need, for example in the trucking and shipping industries, to maintain coverage over wide geographic area without reliance on the presence of a cell phone service.
Satellite-based mobile messaging systems are known that allow the two-way communication of short data messages between a mobile terminal and control center via satellite. Such systems, for example, can send data concerning cargo, such as status and GPS location, back to a command center, and can allow short data messages to be transmitted back to the driver.
A mobile messaging system is described in U.S. Pat. No. 5,991,279, the contents of which are herein incorporated by reference. While this system provides an effective means of communication between remote terminals and a command center using satellite links, the very success of this system means that as the volume of terminals increases, there are increasing demands on available satellite bandwidth. It is thus desirable to utilize bandwidth efficiently in implementing the system. Moreover, since such terminals often travel over a very wide geographic area, for example, across the continental United States or an ocean. Also, power usage is an issue, especially in satellite communications.